2845. ‘Virtual Fossil’ Reveals Last Common Ancestor of Humans and Neanderthals

By Cambridge University, December 18, 201

New digital techniques have allowed researchers to predict structural evolution of the skull in the lineage of Homo sapiens and Neanderthals, in an effort to fill in blanks in the fossil record and provide the first 3D rendering of their last common ancestor. The study suggests populations that led to the lineage split were older than previously thought.

We know we share a common ancestor with Neanderthals, the extinct species that were our closest prehistoric relatives. But what this ancient ancestral population looked like remains a mystery, as fossils from the Middle Pleistocene period, during which the lineage split, are extremely scarce and fragmentary. 

Now, researchers have applied digital “morphometrics” and statistical algorithms to cranial fossils from across the evolutionary story of both species, and recreated in 3D the skull of the last common ancestor of Homo sapiens and Neanderthals for the first time.  

The “virtual fossil” has been simulated by plotting a total of 797 “landmarks” on the cranium of fossilised skulls stretching over almost two million years of Homo history – including a 1.6 million-year-old Homo erectus fossil, Neanderthal crania found in Europe and even 19th century skulls from the Duckworth collection in Cambridge.

The landmarks on these samples provided an evolutionary framework from which researchers could predict a timeline for the skull structure, or ‘morphology’, of our ancient ancestors. They then fed a digitally-scanned modern skull into the timeline, warping the skull to fit the landmarks as they shifted through history.

This allowed researchers to work out how the morphology of both species may have converged in the last common ancestor’s skull during the Middle Pleistocene – an era dating from approximately 800,000 to 100,000 years ago.

The team generated three possible ancestral skull shapes that corresponded to three different predicted split times between the two lineages. They digitally rendered complete skulls and then compared them to the few original fossils and bone fragments of the Pleistocene age.

This enabled the researchers to narrow down which virtual skull was the best fit for the ancestor we share with Neanderthals, and which timeframe was most likely for that last common ancestor to have existed.       

Previous estimates based on ancient DNA have predicted the last common ancestor lived around 400,000 years ago. However, results from the ‘virtual fossil’ show the ancestral skull morphology closest to fossil fragments from the Middle Pleistocene suggests a lineage split of around 700,000 years ago, and that – while this ancestral population was also present across Eurasia – the last common ancestor most likely originated in Africa.

The results of the study are published in the Journal of Human Evolution.    

“We know we share a common ancestor with Neanderthals, but what did it look like? And how do we know the rare fragments of fossil we find are truly from this past ancestral population? Many controversies in human evolution arise from these uncertainties,” said the study’s lead author Dr Aurélien Mounier, a researcher at Cambridge University’s Leverhulme Centre for Human Evolutionary Studies (LCHES). 

“We wanted to try an innovative solution to deal with the imperfections of the fossil record: a combination of 3D digital methods and statistical estimation techniques. This allowed us to predict mathematically and then recreate virtually skull fossils of the last common ancestor of modern humans and Neanderthals, using a simple and consensual ‘tree of life’ for the genus Homo,” he said.  

The virtual 3D ancestral skull bears early hallmarks of both species. For example, it shows the initial budding of what in Neanderthals would become the ‘occipital bun’: the prominent bulge at the back of the skull that contributed to elongated shape of a Neanderthal head.

However, the face of the virtual ancestor shows hints of the strong indention that modern humans have under the cheekbones, contributing to our more delicate facial features. In Neanderthals, this area – the maxillia – is ‘pneumatized’, meaning it was thicker bone due to more air pockets, so that the face of a Neanderthal would have protruded.

Research from New York University published last week showed that bone deposits continued to build on the faces of Neanderthal children during the first years of their life.

The heavy, thickset brow of the virtual ancestor is characteristic of the hominin lineage, very similar to early Homo as well as Neanderthal, but lost in modern humans. Mounier says the virtual fossil is more reminiscent of Neanderthals overall, but that this is unsurprising as taking the timeline as a whole it is Homo sapiens who deviate from the ancestral trajectory in terms of skull structure.

“The possibility of a higher rate of morphological change in the modern human lineage suggested by our results would be consistent with periods of major demographic change and genetic drift, which is part of the history of a species that went from being a small population in Africa to more than seven billion people today,” said co-author Dr Marta Mirazón Lahr, also from Cambridge’s LCHES. 

The population of last common ancestors was probably part of the species Homo heidelbergensis in its broadest sense, says Mounier. This was a species of Homo that lived in Africa, Europe and western Asia between 700,000 and 300,000 years ago.  

For their next project, Mounier and colleagues have started working on a model of the last common ancestor of Homo and chimpanzees. “Our models are not the exact truth, but in the absence of fossils these new methods can be used to test hypotheses for any palaeontological question, whether it is horses or dinosaurs,” he said. 

2844. Neanderthals, the World’s First Misunderstood Artists

By Carl Zimmer, The New York Times, February 22, 2018

A reconstruction of a Neanderthal male based on a skull discovered in Iraq.CreditSebastien Plailly & Elisabeth Daynes/Science Source

It’s long been an insult to be called a Neanderthal. But the more these elusive, vanished people have been studied, the more respect they’ve gained among scientists.

On Thursday, a team of researchers offered compelling evidence that Neanderthals bore one of the chief hallmarks of mental sophistication: they could paint cave art. That talent suggests that Neanderthals could think in symbols and may have achieved other milestones not preserved in the fossil record.

“When you have symbols, then you have language,” said João Zilhão, an archaeologist at the University of Barcelona and co-author of the new study.

When Neanderthal fossils first came to light in the mid-1800s, researchers were struck by the low, thick brow ridge on their skulls. Later discoveries showed Neanderthals to have brains as big as our own, but bodies that were shorter and stockier.

By the early 1900s, scientists were describing Neanderthals as gorilla-like beasts, an extinct branch of humanity that could not compete with slender, brilliant humans.

Yet evidence from both fossils and DNA indicates that Neanderthals and living humans descend from a common ancestor who lived about 600,000 years ago. Our own branch probably lived mostly in Africa.

For a few hundred thousand years after the split, the ancestors of living humans left behind such basic tools as stone axes for butchering carcasses and spear blades for hunting.

But about 70,000 years ago, humans in Africa began showing signs of more abstract thinking. They colored and pierced seashells, for example, possibly to wear as jewelry.

Modern humans began expanding from Africa, arriving in Europe roughly 45,000 years ago. By then, they had become capable of even more impressive symbolic creations, including ivory carvings and extravagant paintings on cave walls.

Neanderthals disappeared abruptly afterward, about 40,000 years ago, leaving behind a fossil record of their own from Spain to Siberia.

Stockier than their African cousins, they appear to have evolved physical adaptations to harsh climates. They made stone tools of their own, which they used to hunt for game, including rhinos and other big mammals.

At first, researchers found no clear evidence of symbolic thought in Neanderthals. But in recent years, that picture has begun to change.

Neanderthals could use feathers and bird claws as ornaments, archaeologists found. But some scientists were skeptical about what these findings meant.

Neanderthals might have lived near modern humans, after all, and spotted them making things. Neanderthals were smart enough to copy the ornaments, the thinking went — but not enough to invent them.

This debate was fueled in part by technological uncertainty: It can be very difficult to pin down a firm date for human fossils and artifacts.

To determine the age of cave paintings, for example, researchers have traditionally relied on radiocarbon dating. But that method only works if the paint contains carbon-bearing ingredients, such as charcoal. Red ocher, by contrast, can’t be dated this way.

Making matters worse, radiocarbon dating becomes increasingly unreliable beyond about 40,000 years.

Dr. Zilhão joined with archaeologists Alistair G.W. Pike of the University of Southampton and Dirk L. Hoffmann, now at the Max Planck Institute for Evolutionary Anthropology in Germany, to see if the prehistory of European art could be brought into sharper focus.

Instead of studying radiocarbon, they would use a different clock to tell time.

As water seeps into caves, it may deposit milky crusts of minerals on the walls known as flowstones. Flowstones contain tiny amounts of uranium, which slowly breaks down into thorium. The older a flowstone gets, the more thorium builds up inside it.

A flowstone covering a piece of cave art might give Dr. Zilhão and his colleagues a minimum age for its creation. The problem was that scientists usually needed big chunks to find enough uranium and thorium to measure. The flowstones on cave art were typically very small.

But Dr. Hoffman had been working on ways to drastically increase the sensitivity of the technology so that he could work with much smaller samples.

The researchers returned to caves in Spain where ancient paintings had been discovered over the past century. The artists had drawn abstract images on the cave walls, including long lines, patterns of dots, and the outline of a human hand.

The team found flowstones covering parts of the artworks and scraped away samples for dating. In three caves, it turned out, some of the art was over 64,000 years

“They must have been made by Neanderthals,” said Dr. Pike.

Wil Roebroeks, an archaeologist at Leiden University who was not involved in the new study, said the evidence was conclusive. “This constitutes a major breakthrough in the field of human evolution studies,” he said. “Neanderthal authorship of some cave art is a fact.”

Dating flowstones is a big advance on previous techniques for determining the age of cave art, but the technology has one major limitation: it can only assign a minimum age to cave paintings. Flowstones may have begun forming the day after a painting was finished — or 10,000 years afterward.

But a second study, which Dr. Zilhão and his colleagues published Thursday in the journal Science Advances, hints that Neanderthals might well have been painting long before 64,000 years ago.

The scientists traveled to a cave on the coast of Spain where Dr. Zilhão had earlier discovered shells that had been drilled with holes and painted with ocher.

In 2010, he and his colleagues had used radiocarbon dating to estimate the age of other shells in the same layer of rock at 45,000 to 50,000 years old.

That result did not tell the team who made the ornaments. Neanderthals might be responsible, but it was also possible that the earliest modern humans in Europe made them.

And the uncertainties of radiocarbon dating also had left open the possibility that the shells were, in fact, far older.

Dr. Zilhão returned to the cave in order to try uranium dating. He and his colleagues discovered a layer of flowstone sitting atop the rock where they had found the shell jewelry. That flowstone turned out to be about 115,000 years old.

The colored, pierced shells themselves are probably not much older than that. Up until about 118,000 years ago, the cave was flooded, thanks to higher sea levels.

That finding provides strong evidence that the shells were made by Neanderthals. They were definitely living in Spain 115,000 years ago, while modern humans would not arrive in Europe for another 70,000 years.

The two new studies don’t just indicate that Neanderthals could make cave art and jewelry. They also establish that Neanderthals were making these things long before modern humans — a blow to the idea that they simply copied their cousins.

The earliest known cave paintings made by modern humans are only about 40,000 years old, while Neanderthal cave art is at least 24,000 years older. The oldest known shell jewelry made by modern humans is about 70,000 years old, but Neanderthals were making it 45,000 years before then.

“These results imply that Neanderthals were not apart from these developments,” said Dr. Zilhão. “For all practical purposes, they were modern humans, too.”

The new studies raise another intriguing possibility, said Clive Finlayson, director of the Gibraltar Museum: that the capacity for symbolic thought was already present 600,000 years ago in the ancestors of both Neanderthals and modern humans.

He agreed with Dr. Zilhão that the new study supports the idea that Neanderthals used language. In addition to the evidence of symbolic thought, researchers have also found that the inner ears of Neanderthals were tuned to the frequencies of speech, much like our own.

“We don’t know how they spoke or what they said,” said Dr. Finlayson. “But they had the ability of speech.”

The cave paintings that Dr. Pike and his colleagues have dated are generally abstract. There’s no evidence so far that Neanderthals painted images of lions and other animals, as modern humans did thousands of years later.

But Dr. Pike doesn’t think a lack of animal imagery marks a mental deficiency in Neanderthals. It could simply reflect a cultural preference.

“It could just be that they had a different belief system and didn’t think animals were important to depict in deep caves,” he said. “If you have to prepare your pigment and get to a place in the pitch dark to paint a red line, that’s as meaningful as someone painting a bison.”

In the past, many researchers have claimed that mental differences between modern humans and Neanderthals were the reason we are alive today and Neanderthal populations have vanished. Our own ancestors, it’s been argued, were able to come up with creative solutions for survival.

The accumulating evidence puts Neanderthals on a more equal footing. They evolved physical differences after the split from modern humans, possibly as they adapted to the harsh northern climates where they settled.

But their culture developed in parallel with that of modern humans in Africa. And their disappearance is not evidence of inferiority, only of the inexorable mechanics of evolution.

“Neanderthals have disappeared. So have Fuegian Indians. So have Greenland Vikings,” said Dr. Zilhão. “Population extinction has been a part of human history forever.”

1717. Skull Fossil Offers New Clues on Human Journey From Africa

By John Noble Wilfred, The New York Times, January 28, 2015

Anthropologists discovered a 55,000-year-old skull fossil in the Manot Cave in western Galilee in 2008, and it was subjected to years of analysis. Photo: Menahem Kahana/Agence France-Presse — Getty Images

Anthropologists exploring a cave in Israel have uncovered a rare 55,000-year-old skull fossil that they say has a story to tell of a reverberating transition in human evolution, at a point when and where some early humans were moving out of Africa and apparently interbreeding with Neanderthals.

The story is of when the Levant was a corridor for anatomically modern humans who were expanding out of Africa and then across Eurasia, replacing all other forms of early human-related species. Given the scarcity of human fossils from that time, scholars say, these ancestors of present-day non-African populations had remained largely enigmatic.

From the new fossil find, which could be closely related to the first modern humans to colonize Stone Age Europe, it appears that these people already had physical traits a bit different from the Africans they were leaving behind and many other human inhabitants along the corridor.

Could this support recent genetic evidence that modern Homo sapiens and their Neanderthal cousins interbred, perhaps in the Middle East and most likely between 65,000 and 47,000 years ago? The discovery team urged caution on the interbreeding issue, but noted anatomical features of the cranium suggesting that some human-Neanderthal mixture had presumably occurred before any encounters in Europe and Asia.

The discovery in Manot Cave in western Galilee, made in 2008 and subjected to years of rigorous analysis, was reported on Wednesday in the journal Nature by an international team of researchers led by Israel Hershkovitz of Tel Aviv University. They said this was “the first fossil evidence from the critical period when genetic and archaeological models predict that African modern humans successfully migrated out of Africa and colonized Eurasia.”

The researchers further concluded that the Manot specimen “provides important clues about the morphology of modern humans in close chronological proximity to a probable interbreeding event with Neanderthals.” They also noted that the shape of the cranium established this as a fully modern human at a time when warmer and wetter conditions were favorable for human migration out of Africa.

In other words, Dr. Hershkovitz said in an interview, the Manot cranium “is the missing connection between African and European populations.”

Scientists not involved with the research team praised the “fascinating new fossil” and the cautious interpretation of its broader implications in understanding the early migrations into Eurasia. “This fossil fits previous predictions,” said Eric Delson, a paleoanthropologist at Lehman College of the City University of New York, “which is a nice rarity in our field.”

Dr. Delson, also a researcher at the American Museum of Natural History, added, “As always, we want more fossils to document variations in and details about this presumed fossil population.”

In an email, Dr. Delson praised the journal authors “for hitting the mark with their analyses and interpretations, reaching all the possible conclusions one could think of: The partial skull combines a basically modern human form with a few features also found in Neanderthals.” In addition, he pointed out, the analysis “supports the similarity of its shapes” to those of modern Africans and early modern humans from Europe, such as the Cro-Magnons.

The partial skull, designated Manot 1, is of a fairly small adult individual, its sex undetermined. The distinctive bunlike shape at the base of the skull resembles modern African and European skulls but differs from other anatomically modern humans from the Levant, and is thus a strong clue that these were among the first humans to settle Europe, scientists said.

Dr. Delson agreed that the evidence “makes it possible that this individual is (or is descended from) a ‘hybrid’ between modern humans and Neanderthals, but as the authors note, such a conclusion cannot be reached from a single fossil, especially as hybrids between species of modern primates usually have some genetically related anatomical oddities.”

One concern is that the fossil skull is fairly small, with a somewhat lower braincase capacity than in modern humans. With only one specimen, it is hard to know whether this is normal for the general population, scientists said. And Dr. Delson said it would be interesting to test for DNA in the skull to support its possible hybrid status in a time of overlapping modern human-Neanderthal populations when early humans were making their way, as he phrased it, to “that small zoological backwater of Eurasia known as Europe.”

Excavations at Manot Cave are expected to continue through at least 2020, searching deeper for more fossils and artifacts from the migrating people. Israel, Dr. Hershkovitz said, “is like a Swiss cheese, lots of caves everywhere.”

Several caves in the vicinity of Manot were occupied for long times by Neanderthals between 65,000 and 50,000 years ago. In this respect, Dr. Hershkovitz said, Manot is an excellent place to search for possible hybrids, but they may be difficult to recognize from surface features. “Only DNA study will solve the problem,” he said.